Biodegradation of organophates \b Studies on horizontal gene transfer of organophosphates degrading gene clster and functional anslysis of mfhA found in plasmid-borne integrative mobilizable element of Sphingobium fuliginis ATCC 27551

Abstract

Xenobiotic compounds in a strict sense can be defined as man-made molecules that have never been exposed to any living organisms before their introduction into an environment. Broadly they are referred as chemicals that are present in significantly higher amounts than natural composition of an environment (TOP and SPRINGAEL 2003). As the chemical ligature found in these compounds are very new to the existing enzymes of living organisms (CASES and DE LORENZO 2001) most of them remain recalcitrant. However, because of the remarkable adaptive nature of the bacteria to extreme conditions of life, considerable numbers of anthropogenic compounds are found to be degradable. According to microbial genetists, three major strategies contribute for bacterial adaptation, rich biodiversity, long-lasting maintenance and development of life on earth (ARBER 2000) [Fig 1-1]. In the first strategy the small local gene sequence changes that occur during the development of a new process contribute for bacterial adaptation. However, in the absence of essential participation of natural selection development of a novel biological function is extremely rare (ARBER 1994). In the second strategy, recombination between related gene sequences results in DNA reshuffling which involves novel combination of existing capacities by the fusion of different functional domains. Third strategy is very efficient phenomenon of genetic variation in which, there is an exchange of evolutionary success between the micro-organisms. Due to such exchange micro-organisms can adapt to a sudden change in the surrounding conditions in a relatively short period of time (OCHMAN et al. 2000) (SPRINGAEL et al. 2002). This phenomenon of acquiring genetic material from neighbouring bacterial species is referred to as Horizontal (Lateral) gene transfer (HGT/LGT). In recent years, wide genome sequencing data available indicated the presence of identical metabolic pathways and enzymes for the degradation of xenobiotic compounds in phylogenetically unrelated bacterial strains isolated from Introduction 3 geographically distinct areas. Such results signifies the existence of similarities in the gene organizations and nucleotide sequences (SENTCHILO et al. 2000; SPRINGAEL et al. 2001) and supports for the of Arber’s third strategy of inter-genomic acquisition (HACKER and CARNIEL 2001)